1. Field of Invention
The present invention relates to the field of medicines and more particularly to a compound of L-setastine hydrochloride and a preparation method therefor.
2. Description of Related Arts
The most common allergic diseases include asthma, allergic rhinitis, hives, allergic dermatitis, and drug allergies, etc., and these common allergic diseases are the major reasons for causing the death of human. Due to the increase of aging population and serious environmental pollutions, the incidence of allergic diseases will be dramatically increased, thereby seriously threatening to the health of the human. The main reason for the incentive of allergic diseases is due to the excitement caused by histamine HI receptors, and therefore, the scientists keep working on research antagonist drugs for HI histamine receptor.
Currently, in clinical application, the most common anti-histamine HI receptor drugs are chlorpheniramine, astemizole, terfenadine, clemastine fumarate, cetirizine hydrochloride and loratadine. Chlorpheniramine has strong sedative side effects, and weak antihistamine effects. The sedative side effects of astemizole and terfenadine are relatively weak, and the onsets thereof are slow, and then the cardiac side effects thereof are strong, so that the practical use of astemizole and terfenadine are stopped by many countries. Clemastine fumarate is an anti-allergy drug, and the anti-cold non-prescription medicines with the compound of clemastive fumarate are on the top three sales in United States. However, the synthesis process of clemastive fumarate is complicated, and key intermediates for synthesizing the clemastive fumarate have to be imported, so that the manufacturing cost is too high to industrial production.
However, the sedative side effects of cetirizine hydrochloride are small, but overdose of cetirizine hydrochloride may cause fatal arrhythmias. Because of complex synthetic process of cetirizine hydrochloride, the crystallizations of the products with cetirizine hydrochloride are difficult. Although, a lot of manufacturer produces cetirizine hydrochloride medicines, but it is difficult to achieve the industrial production. Loratadine has efficiency treatment effects and low in side effects, but the synthesis process thereof is also complicated and high in cost, so that it is difficult for industrial productions.
Setastine hydrochloride is an HI-receptor antagonists with efficient in treatment and low toxicity, and it can inhibit histamine-induced bronchial spasms of guinea pigs. The efficacy time of setastine hydrochloride is longer than that of clemastine. In addition, setastine hydrochloride has no anti-cholinergic and anti-5-serotonin effect after using, and no effects on the cardiovascular system. In other words, it has the same selectivity effects for peripheral H1-receptor as non-sedating antihistamine loratadine.
Comparing with other existing antagonist drug for HI histamine receptors, setastine hydrochloride has the following advantages of:
1. having strong anti-histamine effects, having rapid onset times within 30 minutes after taking, small and slight in side effects, no cardiac side effects, and relieving symptoms for patients having pruritus diseases and resisting to other antihistamines medicines.
2. having small in dose. It is selective to adjust the dosage for using setastine hydrochloride according to the severity of allergy. The dosage thereof is only 1˜4 mg daily. In other words, it has a widely secure daily dosage, which is sixtieth of the daily dosage of terfenadine.
3. having simple in synthesis steps, low in cost, and being able to produce in the to laboratory scale. The cost for producing per kilogram of setastine hydrochloride is the same as that of terferadine. That is to say, in the economic field, setastine hydrochloride has significant advantages comparing with other similar drugs.
Accordingly, setastine hydrochloride was listed in 1987 in Hungary, and was listed in China market after 1987. It was listed in racemic drugs to the China market, and show that it has stronger sedative side effects in clinical use.